The development of OLEDs started in 1987. OLEDs may be classified into low-molecular OLEDs and high-molecular OLEDs. A low-molecular OLED was first proposed by engineers of Kodak Ltd. After three years, high-molecular OLEDs were created in 1990 by researchers of Cambridge University. Thereafter, OLDEs have been separately researched and developed by companies using low-molecular materials and companies using high-molecular materials.
An OLED, which is a current drive-type light emitting device, is advantageous compared to an LCD because it can emit light by itself, can be operated at low voltage, and can be fabricated in the form of a thin film. Since an OLED has a wide viewing angle and a rapid response speed, its image quality does not change and it does not leave behind an afterimage, compared to general LCDs. Therefore, OLEDs can be suitably used for moving image displays. Further, OLEDs have high price competitiveness because their image quality is equal to or exceeds that of an LCD when they are applied to a small-size screen, and the manufacturing process thereof is simple.
However, the disadvantages of OLEDs include a short lifespan and the fact that it is not easy to fabricate a large-size display panel using the OLEDs. Currently, efforts to increase the lifespan of an OLED to 30,000˜50,000 hours are being made, and research into fabricating a large-size display panel using OLEDs is also being done.
Meanwhile, recently, with the trend to develop environment-friendly energy or green energy, technologies for improving energy efficiency have attracted considerable attention in various fields.
Given such background, it is required to develop new and various kinds of lighting devices using an OLED, which has improved energy efficiency.